Chap. XL EVOLUTION. 119 



plete metamorphosis " of the Beetles, Lepidoptera, &c., 

 is of later origin. There were, I believe, perfect 

 Insects before larvae and pupae ; but, on the contrary, 

 Nauplii and Zoeae far earlier than perfect Prawns. In 

 contradistinction to the inherited metamorphosis of the 

 Prawns, we may call that of the Coleoptera, Lepidoptera, 

 &c., an acquired metamorphosis.^ 



" I will here briefly give my reasons for the opinion that the so- 

 called " complete metamorphosis " of Insects, in which these animals 

 quit the egg as grubs or caterpillars, and afterwards become quiescent 

 pupse incapable of feeding, was not inherited from the primitive ancestor 

 of all Insects, but acquired at a later period. 



The order Orthoptera, including the Pseudoneuroptera (Ephemera, 

 Libellula, &c.) appears to approach nearest to the primitive form of 

 Insects. In favour of this view we have : — 



1. The structure of their buccal organs, especially the formation of the 

 labium, " which retains, either perfectly or approximately, the original 

 form of a second pair of maxillae " (Gerstäcker). 



2. The segmentation of the abdomen ; " like the labium, the abdomen 

 also very generally retains its original segmentation, which is shown in the 

 development of eleven segments" (Gerstäcker). The Orthoptera with 

 eleven segments in the abdomen, agree perfectly in the number of their 

 body-segments with the Prawn-larva represented in fig. 33, or indeed, 

 with the higher Crustacea (Podophthalma and Edriophthalma) in 

 general, in which the historically youngest last thoracic segment (see 

 p. 123), which is sometimes late-developed, or destitute of appendages, 

 or even deficient, is still wanting. 



3. That, as in the Crustacea, the sexual orifice and anus are placed 

 upon different segments ; " whilst the former is situated in the ninth 

 segment, the latter occurs in the eleventh " (Gerstäcker). 



4. Their palseontological occurrence ; "in a fossil state the Orthoptera 

 make their appearance the earliest of all Insects, namely as early as the 

 Carboniferous formation, in which they exceed all others in number " 

 (Gerstäcker). 



5. The absence of uniformity of habit at the present day in an order 

 so small when compared with the Coleoptera, Hymenoptera, &c. For 

 this also is usually a phenomenon characteristic of very ancient groups 

 of forms which have already overstepped the climax of their develop- 

 ment, and is explicable by extinction in mass. A Beetle or a Butterfly 

 is to be recognised as such at the fii'st glance, but only a thorough 



